Re: [PATCH v4 1/8] KVM: nVMX: Keep KVM updates to BNDCFGS ctrl bits across MSR write

[Sean Christopherson <seanjc@google.com>]

/cast resurrect

On Fri, Mar 04, 2022, Paolo Bonzini wrote:
> On 3/4/22 00:44, Sean Christopherson wrote:
> > 
> > diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
> > index c92cea0b8ccc..46dd1967ec08 100644
> > --- a/arch/x86/kvm/vmx/nested.h
> > +++ b/arch/x86/kvm/vmx/nested.h
> > @@ -285,8 +285,8 @@ static inline bool nested_cr4_valid(struct kvm_vcpu *vcpu, unsigned long val)
> >  }
> > 
> >  /* No difference in the restrictions on guest and host CR4 in VMX operation. */
> > -#define nested_guest_cr4_valid nested_cr4_valid
> > -#define nested_host_cr4_valid  nested_cr4_valid
> > +#define nested_guest_cr4_valid kvm_is_valid_cr4
> > +#define nested_host_cr4_valid  kvm_is_valid_cr4
> 
> This doesn't allow the theoretically possible case of L0 setting some
> CR4-fixed-0 bits for L1.  I'll send another one.

Ha!  My "patch" is correct.  kvm_is_valid_cr4() calls vmx_is_valid_cr4(), which
calls nested_cr4_valid() when the vCPU is post-VMXON, so it _does_ cover the fixed0
case.  I'll send a proper patch with a comment to call out that subtlety.